Specific requirements are set for valves which are used for regulating and blocking a liquid or gaseous medium under extreme conditions, such as chemical aggression, very high or very low temperatures or under very high pressures. One application for valves which are used for blocking a liquid or gaseous medium under extreme conditions is that of drives in the aerospace field. In this case, the valves are subjected, on the one hand, to extreme temperatures and extreme temperature changes. In the case of valves for liquid and gaseous rocket fuels, there are further parameters such as high mass flow rates, high pressures and short switching times for opening and closing as well as the adoption a predetermined position.
In the aerospace field, a coaxial valve is used for blocking a liquid or gaseous medium, which contains a valve housing comprising an inlet and an outlet for the medium to be blocked, a valve sleeve mounted in the valve housing so as to be longitudinally displaceable in the axial direction between an open position and a closed position and in a sealed relationship with the valve housing, through which the medium to be blocked flows when the valve is open in the longitudinal direction and a closure member arranged coaxial with the valve sleeve at one end of said valve sleeve, against which closure member the valve sleeve bears sealingly in the closed position and from which closure member the valve sleeve is distanced in the open position, opening up a valve opening cross section, and a servo for opening and closing the valve.
A generic coaxial valve of this type is disclosed in DE 199 60 330 A1. In this known valve, the valve sleeve is axially moved relative to the closure member, which is fixed in the flow duct, by means of a lever mechanism which is actuated by an electric or pneumatic servo provided outside the valve housing. In said valve, actuation via the lever mechanism is complex and thus increases the risk of malfunction in a manner which is unacceptable for aerospace applications.
A further coaxial valve is disclosed in DE 10 2005 028 584 A1. In said valve, the valve sleeve is provided on its outer periphery, at least over portions, with a channel-shaped outer helical groove and is surrounded in the portion of the channel-shaped outer helical groove by a drive sleeve which is coaxial with the valve sleeve. The drive sleeve is provided on its inner periphery with at least one channel-shaped inner helical groove which is adapted to the outer helical groove in such a way that the inner and outer helical grooves engage with one another via balls which run in them, and thus form a recirculating-ball gearing of a recirculating-ball spindle drive. The drive sleeve is rotatable in the valve housing, but axially rigidly mounted and subjected to rotational action by a drive motor provided inside the valve housing. The drive motor and the drive sleeve form the drive for the valve sleeve by incorporating the portion integrated in the valve sleeve with the channel-shaped outer helical groove and the balls. The valve sleeve is thus identical to the spindle of the recirculating-ball spindle drive thus formed.
An electro-mechanical coaxial valve is further disclosed in U.S. Pat. No. 6,802,488 B1. Said coaxial valve is unsuitable, however, for the operation of liquid or gaseous media under high pressure and, in particular, unsuitable for cryogenic fluids. A reason for this is that at temperature differences and/or higher pressures the spindle drive may seize up and/or become stiff due to radial pipe expansion. To compensate for this drawback, a powerful servo is therefore required which has a correspondingly high energy requirement.